Issue 41

L. Zhang et alii, Frattura ed Integrità Strutturale, 41 (2017) 356-368; DOI: 10.3221/IGF-ESIS.41.47 361 Take a log-scale for time, get the strength-time regression curve of shotcrete with the traditional accelerator and with the new liquid accelerator, as shown in Fig.3. Figure 3 : Strength-time regression curve of shotcrete added with accelerator. The strength of shotcrete with the traditional accelerator associated with time is determined as -0.38t -0.009t 25.6(1- 1.85e - 0.8e ) c F (t) = (1) The strength of shotcrete with the new liquid accelerator associated with time is determined as      0.18 0.01 ( ) 31.2(1 0.27 0.77 ) t t c F t e e (2) The researcher obtained the following formula of elasticity modulus obtained via tests and shotcrete compressive strength [17]:   5 10 C cu E B A f (3) The fitted values of A and B can be obtained by fitting shotcrete elasticity modulus (listed in Tab. 5) and uniaxial compressive strength by using formula (3) according to the GB50086-2001 Specifications for bolt-shotcrete support . Formula (4) for the relation between shotcrete and compressive strength can be obtained by using formula (3). Shotcrete strength grade C15/MPa C20/MPa C25/MPa C30/MPa Elasticity modulus 1.8x10 4 2.1x10 4 2.3x10 4 2.5x10 4 Uniaxial compressive strength 15.0 20.0 25.0 30.0 Table 5 : Standard values of shotcrete elasticity modulus and uniaxial compressive strength. 5 10 46.12 2.46   C cu E f (4)